Need some help figuring out what to do....

I was just given a 14' x 24' Leonard metal garage. It has already been wired with overhead lights,
outlets, wall switches, exhaust fans and two 240volt outlets. It's got an old (funky looking) panel with
two 15 amp breakers. The building has been moved to my property (I live in the county) and is just at
150' from the house, which, happens to have the electric meter, and a panel with three breakers; one for
our well pump, one for the hot water heater, and a 30 amp breaker for a "steamer" attached to the wall.

My question: can I run wire from the outside panel (using the 30 amp breaker for the "steamer") to this
building? If so, do you think I should replace the panel with the two 15 amp breakers in the garage with a
new panel? Should I run what size wire from the house and should it be in conduit? PVC okay?

First step is to do a calculation of the power needed for the building. Second step is to size the four wire feeder by this load using 225.39
225.39 Rating of Disconnect.
The feeder or branch-circuit disconnecting means shall have a rating of not less than the calculated load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits, Part III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. Where the branch circuit or feeder disconnecting means consists of more than one switch or circuit breaker, as permitted by 225.33, combining the ratings of all the switches or circuit breakers for determining the rating of the disconnecting means shall be permitted. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D).
(A) One-Circuit Installation. For installations to supply only limited loads of a single branch circuit, the branch circuit disconnecting means shall have a rating of not less than 15 amperes.
(B) Two-Circuit Installations. For installations consisting of not more than two 2-wire branch circuits, the feeder or branch-circuit disconnecting means shall have a rating of not less than 30 amperes.
(C) One-Family Dwelling. For a one-family dwelling, the feeder disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
(D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.

When installing this disconnect at the building we must also adhere to 225.36
225.36 Suitable for Service Equipment.
The disconnecting means specified in 225.31 shall be suitable for use as service equipment.

Don’t forget that this disconnect is required to be connected to an electrode system as outlined in 250.32
250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).
(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.

If you decide to install rods at this building it will require two rods as outlined in 250.53(A)(2)
(2) Supplemental Electrode Required. A single rod, pipe, or plate electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). The supplemental electrode shall be permitted to be bonded to one of the following:

When dealing with remote buildings on our property we must remember that what works may not be safe. There is only one way to install this system in a safe manner as outlined in this post.

The panel and wiring that is in the building must go. It is nothing less than a fire waiting to get started. To ensure a compliant installation be sure to permit and get it inspected for your protection. To fail to follow the proper procedures could result in a loss of homeowner’s insurance for your home.